The present invention relates to a holder for holding a blood sample tube, and more particularly to a blood sample tube holder for preventing a kickback in a blood sample tube having a small resistance to being pierced by a needle, i.e., a small piercing resistance.
Blood sampling systems are used in clinical examination in hospitals or other medical facilities. In such blood sampling systems, a blood sample tube holder is combined successively with various blood sample tubes such as those for use examining blood serum, blood cells, blood sugar, and coagulants, and blood samples are obtained from a patient through a multiple needle mounted on the blood sample tube holder and collected in the blood sample tubes, respectively.
A blood sample tube, such as a decompressive blood sample tube, comprises a bottomed tube of glass or plastics and a rubber plug in the bottomed tube.
In use, a decompressive blood sample tube of such a construction is inserted into a cylindrical blood sample tube holder, and a rubber piercing portion of a multiple needle penetrates the rubber plug of the blood sample tube. The rubber plug which the rubber piercing portion of the multiple needle pierces is relatively thick as it is required to have a gas barrier and a resealing capability. Since the rubber plug presents a strong resistance to being pierced by the rubber piercing portion, the tendency of the decompressive blood sample tube to return to its original position immediately after the rubber plug is pierced by the needle, i.e. a phenomenon called a "kickback", is small.
If an automatic blood serum separator is used, it is preferable to employ a decompressive blood sample tube which can be used without detaching its rubber plug.
FIG. 1 of the accompanying drawings shows a decompressive blood sample tube 10 proposed by the applicant. The decompressive blood sample tube 10 comprises a bottomed tube 2 and a sealing assembly 8 placed over the open end of the bottomed tube 2 and composed of a film member 4 and a resealing rubber member 6. In use, the needle of an automatic blood serum separator directly pierces the sealing assembly 8. The proposed decompressive blood sample tube 10 does not employ any rubber plug, but is prevented from getting contaminated from an external source. The decompressive blood sample tube 10 is inserted in a cylindrical blood sample tube holder 14 with a multiple needle 12 mounted thereon The multiple needle 12 comprises a blood vessel piercing portion 16, a rubber piercing portion 20 projecting into the holder 14 and covered with a rubber sheath 18, and a needle base 22 supporting the blood vessel piercing portion 16 and the rubber piercing portion 20 on its opposite ends. When the multiple needle 14 is inserted into the blood sample tube holder 14, the rubber piercing portion 20 penetrates the rubber sheath 18 and the sealing assembly 8. Blood drawn from the patient through the blood vessel piercing portion 16 flows through the multiple needle 12 into the decompressive blood sample tube 10.
The film member 4 provides a gas barrier capability whereas the resealing rubber member 6 provides a resealing capability. Because the resistance presented by the sealing assembly 8, which is used in place of a conventional rubber plug, to being pierced by the rubber piercing portion 20 of the multiple needle 12 is generally weak, the decompressive blood sample tube 10 is subject to a kickback under the resiliency of the rubber sheath 18 on the rubber piercing portion 20, and the sealing assembly 8 may not be sufficiently pierced by the rubber piercing portion 20 of the multiple needle 12.
To prevent such a kickback, it is necessary to keep the outer wall surface of the sealing assembly 8 or the bottomed tube 2, or a flange 24 of the bottomed tube 2, firmly fitted in the blood sample tube holder 14. One arrangement for meeting this requirement is to provide ribs on the inner wall surface of the holder 14 for secure fitting engagement with the bottomed tube 2. According to this structure, the force required to fit the decompressive blood sample tube 10 into the blood sample tube holder 14 tends to be excessively increased, and a certain increased level of finishing accuracy is required of the holder 14 and the tube 10 to maintain the force required to fit the tube 10 into the holder 14 at a certain constant level. More specifically, for collecting a blood sample from a patient, the blood vessel piercing portion of the multiple needle 12 mounted on the holder 14 is inserted into a blood vessel of the patient, and then the decompressive blood sample tube 10 is inserted into the blood sample tube holder 14 until the rubber piercing portion 16 of the multiple needle 12 penetrates the sealing assembly 8. While the tube 10 is being inserted into the holder 14, the force required to fit the tube into the holder 14 may be abruptly increased, or a large force may be needed to pull the tube 10 out of the holder 14 after a blood sample is obtained in the tube 10. The increased level of finishing accuracy required of the holder 14 and the tube 10 results in an increase in the cost of manufacture of blood sample tube holders and blood sample tubes.